Qlikview architecture depends upon in what context it is asked. It can be the system architecture or data architecture.
System architecture can be classified by what all components comes under Qlikview development (Qlikview desktop), deployment (QVS), publishing (Publisher), Analysis (Access Point). Data architecture specify that how many layers have been created in an application like
Single tier ( One qvw fetching data, transforming data, creating datamodel and UI), two tier, three tier, three tier mixed etc.
Hope this helps.